In heart surgery, a cardiopulmonary bypass device is used when causing the heartbeat of a patient to cease and taking the place of the heart to perform the respiration and circulation functions during the cessation of the heartbeat. Further, during the surgery, in order to reduce the amount of oxygen to be consumed by the patient, it is necessary to lower the body temperature of the patient and maintain the lowered temperature. Therefore, the cardiopulmonary bypass device is provided with a heat exchanger for controlling the temperature of blood collected from the patient.
As such a medical heat exchanger, conventionally, a bellows tube type heat exchanger and a multitubular heat exchanger (see, for example, Patent Document 1) are known. Of them, the multitubular heat exchanger has an advantage of a higher heat exchange efficiency compared with that of the bellows tube type heat exchanger, because the multitubular heat exchanger can obtain a larger heat exchange area, assuming that the volume of the multitubular heat exchanger is the same as that of the bellows tube type heat exchanger.
A conventional exemplary multitubular heat exchanger will be described with reference to FIGS. 20A-20C. FIG. 20A is a top view of a multitubular heat exchanger, and FIG. 20B is a side view thereof. FIG. 20C is a perspective view illustrating an inside of a housing of the heat exchanger, which is illustrated partially in a cross-section.
The heat exchanger includes a thin tube bundle 102 composed of a plurality of heat transfer thin tubes 101 allowing cool/warm water that is heat medium liquid to flow, seal members 103a-103c sealing the thin tube bundle 102, and a housing 104 containing these components.
A plurality of the heat transfer thin tubes 101 are arranged in parallel and stacked to form the thin tube bundle 102. As illustrated in FIGS. 20A and 20C, the seal member 103c at the center is provided with a blood channel 105 having a circular cross-section at the center in a longitudinal direction of the thin tube bundle 102. The blood channel 105 functions as a heat exchange channel for distributing blood that is liquid to be subjected to heat exchange so that the blood comes into contact with each outer surface of the heat transfer thin tubes 101. The seal members 103a, 103b at both ends respectively expose both ends of the thin tube bundle 102.
As illustrated in FIG. 20B, the housing 104 has a blood inlet port 106 for introducing blood into the housing 104 and a blood outlet port 107 for discharging the blood out of the housing 104, which are placed at upper and lower ends of the blood channel 105. Further, gaps 108 are provided between the seal members 103a-103c respectively. The housing 104 is provided with leaked liquid discharge holes 109 corresponding to the gaps 108.
In the above-mentioned configuration, blood is allowed to flow in from the blood inlet port 106 and flow out of the blood outlet port 107 after passing through the blood channel 105. Simultaneously, as illustrated in FIGS. 20A and 20B, cool/warm water is allowed to flow in from one exposed end of the thin tube bundle 102 and flow out of the other exposed end thereof. Thus, the heat exchange is performed between the blood and the cool/warm water in the blood channel 105.
The gaps 108 are provided for the purpose of detecting leakage when the blood or cool/warm water leaks due to seal leakage. More specifically, when leakage from the third seal member 103c occurs, the leaked blood appears in the gaps 108 and thus, the leakage can be detected. Further, even when the cool/warm water leaks due to the leakage from the first seal member 103a or the second seal member 103b, the leaked cool/warm water appears in the gaps 108, and thus, the leakage can be detected. The blood or cool/warm water having leaked in the gaps 108 is discharged outside of the heat exchanger from the leaked liquid discharge holes 109.    Patent Document 1: JP 2005-224301 A